This invention relates to the field of data storage and retrieval. More particularly, it relates to improvements in apparatus of the type which is adapted to store a relatively large number of data storage disks (e.g., disks of the optical, magnetic and magneto-optic variety) and, on command, to transport a selected disk between a storage location and a disk utilization device, such as a disk drive.
Automated disk libraries, sometimes known as "juke-boxes", are known in the art for storing and utilizing a large number of data storage disks. Examples of such libraries are those disclosed in U.S. Pat. Nos. 4,286,790; 4,504,936; 4,608,679; and 4,614,474. In such libraries, each data storage disk is housed in a protective cartridge or carrier which surrounds the disk and facilitates disk-handling. The disk carriers are supported by one or more storage racks or the like which serve to arrange the carriers in closely spaced parallel planes, either side-by-side, or one above the other. Such systems comprise one or more disk drives for playing and/or recording information on the disks, and a disk carrier transport mechanism for transporting selected disks between their respective storage locations and the disk drive unit(s). The disk carriers are commonly provided with a pair of spaced notches or gripping slots on or near one edge so that the cartridges can be readily gripped and removed from their assigned storage positions or from their standby positions within a disk drive. In some systems, the disk carrier transport mechanism includes means for selectively rotating or flipping the disk carrier 180.degree. so that either side of the data storage disk can be presented to the disk drive for recording and/or playback.
In data storage systems of the type disclosed in the aforementioned patents, each disk carrier must be inserted into the disk storage rack in a predetermined orientation so that its respective gripping slots are accessible to the transport mechanism. If the disk carrier orientation is altered, e.g., the carrier is turned end-for-end, it would be impossible for the carrier transport mechanism to grip the carrier for subsequent transport. While such systems are designed to avoid any such undesired change in disk carrier orientation, they do so at the expense of increasing the mean time to change disks. For example, a disk may have to be reoriented between the time it is removed from a disk drive and the time it is returned to storage.